Abnormalities in motor conduction in vitamin B12 deficiency.

Three patients with vitamin B12 deficiency were studied to determine the extent of the disturbance of nerve conduction. All had small or absent sural potential and in addition all had some abnormalities of F response. Motor nerve conduction in legs was borderline or abnormal and in two patients there were some features of a mononeuritis multiplex syndrome. Abnormalities of motor conduction are thus part of the changes in vitamin B12 deficiency in addition to the involvement of the sensory nerves.